Investigating herds with lameness problems (Proceedings)
Many dairy herds have unusual or exceptionally serious lameness problems. The paper describes a systematic way to approach and evaluate such problems based on published observations of risk factors for specific disease problems and the author's experience. It is important to define an etiologic diagnosis since preventive or corrective measures will depend on the cause of the herd problem. Compound etiologies and complex risk factor interactions are the norm in this sometimes frustrating endeavor.
Data and Definition of the Problem.
The characteristics reported by the owner or herd manager may be adequate to generally describe the process occurring in the herd. More often, examination of several cows with what is considered the primary problem will be required to define the nature of the lesions and establish an etiologic diagnosis. The nomenclature for lameness lesions and causes varies widely. Many times all lameness cases are called footrot or abscesses regardless of the true nature of the lesions responsible.The magnitude of the problem is important when formulating a plan. Data from health records or hoof trimmer score sheets should be consulted. It is desirable to examine data covering a significant historical period if such data is available. Since some problems are linked to seasonal changes in climate, feeding, or management, 24 months of data would be most useful. Many times the only data available are an impression or the recollections of the owner or manager. This type of data, however sincerely held, is most difficult to assess. Further, the response to any corrective actions proposed will be measured against current data.
Recommended data include the cow ID, date of treatment or trimming, lesion or diagnosis, and treatment administered. Usually there are two sources of data. The individual cow records kept by the dairyman of treatments by him or the veterinarian and the records of the hoof trimmer. The quality and thoroughness of this data are quite variable. Providing data recording sheets for trimmers and herdsmen in the form of a checklist for common lesions can create a useful database if they are not already using a system that allows later analysis. In one problem herd without individual cow records where treatments were done by the herdsman, I was able to estimate the magnitude of the problem month by month by checking invoices for hoof blocks purchased during the preceding year. For computerized records, such as Dairy Comp 305, the dated events TRIM or LAME if followed by comments regarding diagnosis or treatment can be readily analyzed.
If data are not available, then examination of the entire herd or a proportional sample of each of the groups within the herd should be done. Depending on the nature of the problem, it may require scoring locomotion, posture, or the presence of specific lesions only revealed after restraint of the cow in a chute or on a tilt-table and cleaning the digits or paring of the soles. Scoring cows at the walk as they exit the milking parlor is the norm. There are a number of locomotion scoring systems described and most use 4 or 5 categories of severity. When conducting a herd evaluation I usually score only as OK or in need of attention. This simplifies the final assessment. For scoring heel horn erosion or digital dermatitis it may be possible to assess these in the milking parlor with a flashlight. These examinations of the herd aim to answer the questions of who demographically is affected (stage of lactation, parity, housing group), what proportion of the herd is affected, and what lesions or diseases are most prominent.
It may be useful to create a photographic record of the lesions or of other important features of the environment. Digital images also allow communication of observations to others for evaluation or comment.
Classification of Herd Problem by Etiology.
Major herd problems will fall into one of several main categories: infectious digital disease, laminitis/coriosis, and overworn/trauma. Specific risk factors for the problem identified as primary in the herd should be examined. Conclusions about the relative importance of each risk factor and the appropriate corrective or prophylactic measures comprise the main effort in correcting the herd problem.
Control programs should be capable of maintaining the incidence of cases requiring individual animal treatments below 2% of cows at risk per year. Incidence rates in excess of this mean interdigital skin injury beyond the simple maceration due to the constant exposure to moisture in freestall environments or an ineffective control effort. This may be from small stones in inorganic bedding or walking through stony laneways or mudholes outside. There may be additional risk due to interdigital fibromas from chronic interdigital dermatitis which can lead to secondary injury of the interdigital skin by trauma. There may be abnormally high infection pressure due to slurry or mud coating of the extremities.
Control measures usually require a combination of hygiene and prophylaxis. Hygiene may be accomplished by more frequent manure removal from freestall barns or redesigning laneways to avoid trauma and reservoirs of infection. Prophylaxis is usually with footbaths.